Method and Apparatus for Delivering Keying Information

1. A method of delivering an application key or keys to an application server for use in securing data exchanged between the application server and a user equipment, the user equipment accessing a communications network via an access domain, the method comprising: running an Authentication and Key Agreement procedure between the user equipment and a home domain in order to make keying material available to the user equipment and to an access enforcement point, and using at least a part of said keying material to secure a communication tunnel between the user equipment and the access enforcement point; deriving one or more application keys within the home domain using at least part of said keying material, providing said application key(s) to said application server, and deriving the same application key(s) at the user equipment, wherein said access enforcement point is unable to derive or have access to said application key(s).

2. The method according to claim 1 , wherein the running of said Authentication and Key Agreement procedure occurs at registration or re-registration of the user equipment with the home domain.

3. The method according to claim 1 , wherein domain access via said access enforcement point is controlled by an access enforcement point controller, said step of running an Authentication and Key Agreement procedure between the user equipment and a home domain comprising: sending from the home domain to the access enforcement point controller an authentication vector including a random value, and secondary cipher and integrity keys derivable from the random value, and forwarding the random value to the user equipment; passing the secondary cipher and integrity keys from the access enforcement point controller to the access enforcement point; and at the user equipment, applying a first key derivation function to the random value to generate primary cipher and integrity keys, and applying a second key derivation function to the primary cipher and integrity keys to generate said secondary cipher and integrity keys, whereby a secure tunnel can be established between the access enforcement point and the user equipment on the basis of said secondary cipher and integrity keys.

4. The method according to claim 3 and comprising deriving said application keys(s) at the user equipment and at the home domain using one or both of said primary cipher and integrity keys.

5. The method according to claim 1 , wherein domain access via said access enforcement point is controlled by an access enforcement point controller, said keying material comprising first and second random values and primary cipher and integrity keys derivable from the first random value, the method comprising: forwarding the random values from the access enforcement point controller to the user equipment, and the user equipment applying a first key derivation function to the first random value to generate primary cipher and integrity keys, whereupon a secure tunnel can be established between the access enforcement point and the user equipment on the basis of said primary cipher and integrity keys.

6. The method according to claim 5 and comprising deriving said application key(s) at the user equipment and within the home domain using said second random value.

7. The method according to claim 6 and comprising deriving secondary cipher and integrity keys from the second random value, and then applying a key derivation function to the secondary cipher and integrity keys to generate the application key(s).

8. The method according to claim 5 , said steps of deriving an application key or keys within the home domain and at the user equipment comprising utilizing a secret shared between the home domain and the user equipment to derive the application key(s).

9. The method according to claim 1 and comprising deriving said application key(s) by applying a key derivation function to cipher and integrity keys, and to a service node identifier.

10. The method according to claim 1 , wherein said access enforcement point is within a Proxy Call Session Control Function of an IP Multimedia Subsystem.

11. The method according to claim 10 , wherein said access enforcement point controller is provided within the Proxy Call Session Control Function, and, within the home domain, a Serving Call Session Control Function is responsible for handling said Authentication and Key Agreement procedure in conjunction with a Home Subscriber Server.

12. The method according to claim 1 , wherein said access enforcement point is within a Serving GPRS Support Node of a UMTS access domain.

13. The method according to claim 12 , wherein said access enforcement point controller is provided within the Serving GPRS Support Node.

14. The method according to claim 1 , wherein said access enforcement point is within a Radio Network Controller of a UMTS access domain.

15. The method according to claim 14 , wherein said access enforcement point controller is provided within a Visitor Location Register.

16. The method according to claim 1 , wherein said access domain comprises a Long Term Evolution access domain, said access enforcement point being a UPE/MME/eNodeB.

17. The method according to claim 16 , wherein said access enforcement point controller is provided within a MME.

18. The method according to claim 16 comprising interposing a user credential management server between a Home Subscriber Server of the home domain and the access enforcement point controller, this server determining secondary cipher and integrity keys and providing application keys to application servers upon request.

19. A network based apparatus for delivering an application key or keys to an application server for use in securing data exchanged between the application server and a user equipment, the user equipment accessing a communications network via an access domain, the apparatus comprising: means for running an Authentication and Key Agreement procedure with the user equipment in order to make keying material available to the user equipment and to an access enforcement point, whereby at least a part of said keying material can be used to secure a communication tunnel between the user equipment and the access enforcement point; means for deriving one or more application keys using at least part of said keying material, and providing said application key(s) to said application server, the keying material allowing the user equipment to also derive the application key(s) but not allowing said access enforcement point to derive the key(s).

20. A method of securing communications between User Equipment and an application server via an IP Multimedia Subsystem network, the method comprising: running an Authentication and Key Agreement procedure between the User Equipment and a Serving Call State Control Function of the IP Multimedia Subsystem network in order to make available to the User Equipment and to a Proxy Call State Control Function, keying material, and using at least a part of said keying material to secure a communication tunnel between the User Equipment and the Proxy Call State Control Function; and deriving at least one application service key at the Serving Call State Control Function using at least part of said keying material, providing said application service key(s) to said application server, and deriving the same application service key(s) at the User Equipment, wherein the Proxy Call State Control Function is unable to derive said application service key(s).

21. The method according to claim 20 , wherein said keying material comprises a random value, and second cipher and integrity keys derivable from the random value, the method comprising providing these values to the Proxy Call State Control Function from the Serving Call State Control Function, the Proxy Call State Control Function forwarding the random value to the User Equipment, and the User Equipment applying a first key derivation function to the random value to generate first cipher and integrity keys, and applying a second key derivation function to the first cipher and integrity keys to generate said second cipher and integrity keys, whereupon a secure tunnel can be established between the Proxy Call State Control Function and the User Equipment on the basis of said second cipher and integrity keys.

22. The method according to claim 21 , wherein said second cipher and integrity keys are derivable from the random value and from a secret shared between the User equipment and the Serving Call State Control Function or a node couple to the Serving Call State Control Function.

23. The method according to claim 21 comprising deriving said application service key(s) at the User Equipment and at the Serving Call State Control Function using one or both of said first cipher and integrity keys.

24. The method according to claim 20 , wherein said keying material comprises first and second random values and first cipher and integrity keys derivable from the first random value, the method comprising forwarding the random values from the Proxy Call State Control Function to the User Equipment, and the User Equipment applying a first key derivation function to the first random value to generate first cipher and integrity keys, whereupon a secure tunnel can be established between the Proxy Call State Control Function and the User Equipment on the basis of said first cipher and integrity keys.

25. The method according to claim 24 , wherein said application service key(s) is(are) derived at the User Equipment and at the Serving Call State Control Function using said second random value.

26. The method according to claim 25 comprising deriving second cipher and integrity keys from the second random value, and then applying a key derivation function to the second cipher and integrity keys to generate the application service key(s).

27. The method according to claim 20 , said steps of deriving an application service key or keys at the Serving Call State Control Function and at the User Equipment comprise utilizing a secret shared between the Serving Call State Control Function, or a node coupled to the Serving Call State Control Function, and the User Equipment to derive the application service key(s) from at least part of said keying material.

28. The method according to any one of claim 20 , wherein said application service key(s) is(are) derived by applying a key derivation function to cipher and integrity keys, and to a service node identifier.

29. User Equipment for establishing a secure communication link with an application server via an IP Multimedia Subsystem, the method comprising: means for running an Authentication and Key Agreement procedure with a Serving Call State Control Function of the IP Multimedia Subsystem network in order to make available to the User Equipment and to a Proxy Call State Control Function, keying material, and for using at least a part of said keying material to secure a communication tunnel between the User Equipment and the Proxy Call State Control Function; means for deriving at least one application service key using at least part of said keying material, wherein the Proxy Call State Control Function is unable to derive said application service key(s); and means for establishing a secure communication link with said application server using said application service key(s).

30. The method of claim 1 , wherein the Application Server is located within the home network of the User Equipment.

31. The method of claim 10 , wherein the Application Server is located within a visited network.

32. A method of delivering an application key or keys to an application server for use in securing data exchanged between the application server and user equipment communicating over a network, the user equipment accessing a communications network domain via an access enforcement point, the method comprising the steps of: running an Authentication and Key Agreement procedure between the user equipment and a home domain in order to make primary keying material available to the user equipment and to the home domain; deriving, at the user equipment and at the home domain, secondary keying material and a stored base key from said primary keying material and providing the access enforcement point with said secondary keying material and using at least a part of said secondary keying material to secure a communication tunnel between the user equipment and the access enforcement point; receiving at the home domain a request for application service key, the request at least comprising an identifier of requesting application server and an identifier of said base key; deriving within the home domain and at the user equipment, from the identified base key, one or more application service keys at least dependent on the identifier of said server; and providing said application service key(s) to said application server, wherein said access enforcement point is unable to derive or have access to said application service key(s).

33. A method of delivering an application key or keys to an application server for use in securing data exchanged between the application server and user equipment communicating over a network, the user equipment accessing a communications network domain via an access enforcement point, the method comprising the steps of: running an Authentication and Key Agreement procedure between the user equipment and a home domain in order to make primary keying material available to the user equipment and to the home domain; deriving, at the user equipment and at the home domain, secondary keying material and a stored base key from said primary keying material and providing the access enforcement point with said secondary keying material and using at least a part of said secondary keying material to secure a communication tunnel between the user equipment and the access enforcement point; receiving at the home domain a request for application service key, the request at least comprising an identifier of requesting application server and an identifier of said base key; deriving within the home domain and at the user equipment, from the identified base key, one or more application service keys at least dependent on the identifier of said server; providing said application service key(s) to said application server; wherein said access enforcement point is unable to derive or have access to said application service key(s); wherein said access enforcement point is within a Serving GPRS Support Node of a UMTS access domain, or within a Radio Network Controller of a UMTS access domain, or a UPE/MME/eNodeB wherein said access domain comprises a Long Term Evolution access domain.